1. Field of the Invention
The present invention relates to a power supply, and in particular to a dual-input power supply with adjustable outputted voltage.
2. Description of Prior Art
A power supply with dual-input power sources has an AC power input and a DC power input, and it converts these two inputted power sources into a DC voltage output for subsequent use. As a result, this kind of power supply can be used indoors or outdoors.
U.S. Pat. Nos. 5,901,056 and 6,650,560 disclose a conventional power supply with dual-input power sources respectively. When the power supply disclosed in each of the-above mentioned patents is in use, an AC power plug is inserted into an indoor AC wall power socket, so that the AC power input can be converted into a DC power input via an AC power processing circuit provided in the power supply. When the power supply with dual-input power sources is taken to the outdoors, a DC plug (such as a plug of a cigarette lighter) can be inserted into a DC power socket of a car. After the DC power is inputted into the power supply and is converted by the DC power processing circuit, the converted power can be supplied for the subsequent use.
The conventional power supply with dual-input power sources has a main transformer in the AC power input processing circuit. Further, it also has a fuse in order to protect against an extremely large current and isolate the circuit. However, the conventional power supply with dual-input and outputted power sources has no protection design in the DC power input processing circuit. As a result, if an extremely large current is inputted to the DC power input end, the loaded electronic device at the user's end may suffer damage.